I have a problem with the carb on my '21 Touring. The car runs great so I don't want to change carbs. I bought a new air/fuel adjusting needle and the locking nut for it from Lang's quite some time back. I have misplace the old parts that I removed. My problem is I cannot find the right place to leave the setting on the nut. If I leave it set so the needle turns freely the nut will loosen up, if I tighten it where it will not loosen up the needle is hard to turn. I guess I will remove the needle and nut and make sure the needle turns freely in the nut while I hold them in my hand. If so, I wonder about deforming the threads on the nut slightly so it won't turn as easily in the carb body. Anybody else had the same problem?
Tommy, the nut is split and the thread is tapered for a reason. As it is turned in it clamps around the needle shaft. It is supposed to be firm enough to stop the needle winding itself in/out.
Once you have the carburetor set for optimal performance, it is rare that further adjustment is necessary, so you can firm up the nut and forget.
Others do like to fritz with the mixture control, so their opinions may vary.
Hope this helps.
Allan from down under.
Thanks Allan. I have developed the habit of opening the screw one full turn from where it normally runs when cold starting. I usually do so by turning the screw at the carb, when I open the hood to open the gas valve. I can stop doing so as I'm not sure that it is necessary, though it seems to make the engine run smoother for the first minute or so after starting.
I always open the screw 1/2 turn to start cold and close it once the car starts. By the time I get from the crank to the spark lever I can usually move it back unless it is very cold out. I keep the nut just tight enough to keep the adjusting rod in place but loose enough to turn by hand. I have a mark on the adjusting knob to use as a reference so I can return the needle to the same position each time.
I leave mine set in the same place. However when I tour in the higher elevations, like the Rocky Mountains, I have to lean it out. Here in Southern California the weather stays pretty constant, so I rarely ever need to adjust it.
Sounds like you and I run to the same program Larry. Set and forget. I don't even compensate for altitude, our tallest mountain reaching a majestic 2800'
Allan from down under.
I'm of the opinion it was meant to be able to be adjusted. Otherwise, there wouldn't be a control on the dash. It would be like the idle speed screw and only be accessible from under the hood.
Tommy, your idea may work, but I wonder if the judicial use of a removable thread locker might work better. You'd have to make sure it didn't lock the needle to the carb. I'd be afraid that "squishing" the nut would make it hold the needle tighter in some places and not as tight in others. But that's pure speculation.
This may be a really stupid idea but what about a very tiny drop of blue LokTite on the threads.
Hal, you are correct that the mixture is meant to be adjustable, from the cockpit at that. What Larry and I suggest is that once adjusted, it doesn't need re-adjustment. That of course varies with conditions, and that is not something with which I am familiar.
My 1912 van running a Holley H1 was giving me grief with a persistent miss unless under load. I pulled the plugs and cleaned them. They were a little on the dark side. The cleaning made no difference. While waiting for time to expire so I could park in a city clearway, I decided to lean the mixture off a little to see if that helped. Lo and behold, the idle evened out, the miss went away and I was a happy camper. Someone at one of my stops must have had a play with the mixture screw!!!
Now I am back to set and forget.
Allan from down under.
I have had success in the past using tooth
paste to increase the friction of threads. Paint it on the threads and let it dry, then assemble.
I've had luck simply tightening the clamp nut a bit...the difference between slack and snug is just a few degrees of rotation...it's split and is a pipe thread. It WILL tighten down on the mixture screw.
My experience has generally been, that with the adjustment where the car runs best, it is usually very hard to start. Pre-start adjustment, followed by a running adjustment is my usual routine. I say "generally been" because I have known people that do set-it and forget-it, and actually had a couple Ts that were basically able to do that most of the time myself.
I think it could be interesting to keep an eye on which carburetors are doing what. Allan B does mention his '12 with the Holly H1, which is a carburetor most of us will never use ourselves.
A few of my Ts over the years had era after-market carburetors, which may be of less interest here. Most of all the others I have run Holly NH carburetors. With one exception, they all ran very well and were quite reliable. And all behaved as though richening were needed for starting a cold engine.
I have had, but never run any Kingston myself.
If I leave the setting on my '21 alone, where it runs best, the car tends to start but die before I can get to the spark lever to advance it to keep the engine running. It does take me just a bit longer to reach it than some, because of my handicap. If I open the needle valve a bit it continues running long enough for me to reach it.
Wayne and Tommy, that has been my experience as well. I find that richening the mixture about 1/2 turn before starting will usually keep it running, where not doing it, it burns up the initial charge from choking and then dies. Some might say, just choke more, but both my NH's will flood if choked more than one pull of the crank. I hear some folks say they choke for 4 pulls of the crank to get fuel to all 4 cylinders. If I choked for 4 pulls, I'd have fuel running out on the shop floor. Guess they are all different.
I like Scott's idea about toothpaste. I may try that one day on something that needs a dry thread locker. I like Michael's idea too. Why didn't I think of that?
Mark, you serious about the toothpaste?
Yes, sometimes it gives just enough extra grip to the parts so that they will hold their position.
I have a mountain bike (bicycle) with an adjustable height seat post. The post would slowly sink down into the frame during a ride, no matter how tight I made the clamp. Some tooth paste on the post, and it has held its setting for years now.
If it doesn't work, you can just clean it off with water and a tooth brush!
Note that Mark said let it dry before assembling.
If the needle is easy to turn, it will vibrate off its adjustment after several miles. It's supposed to be stiff, not loose & not tight. As Scott suggests, it's kind of a finicky thing to get "just right". Make very small adjustments to the nut until you get the needle snug.
Most tooth paste is a mild abrasive in a suspension. Luckily the brass nut has lots of metal and the slits to allow it to be adjusted pretty far. You could use a little rottenstone mixed with water or oil if you do wood working and happen to have it. Iíve never had any problem with that adjustment over the years and I fiddle with my needle adjustment frequently.